Release evacuation candidates after parallel sweeper threads completed.

src/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 517 matching lines @@
 
 
 void MarkCompactCollector::StartSweeperThreads() {
   sweeping_pending_ = true;
   for (int i = 0; i < FLAG_sweeper_threads; i++) {
     heap()->isolate()->sweeper_threads()[i]->StartSweeping();
   }
 }
 
 
-void MarkCompactCollector::WaitUntilSweepingCompleted() {
+bool MarkCompactCollector::WaitUntilSweepingCompleted() {

[Michael Starzinger, 2013/02/21 12:22:09]

Why do you return a boolean here? IMHO this makes the call sites too complex, I
would just rely on FinalizeSweeping() to be a no-op in those cases. I'll leave
that up to you.

[Hannes Payer (out of office), 2013/02/21 12:52:31]

Done.

   if (sweeping_pending_) {
     for (int i = 0; i < FLAG_sweeper_threads; i++) {
       heap()->isolate()->sweeper_threads()[i]->WaitForSweeperThread();
     }
     sweeping_pending_ = false;
     StealMemoryFromSweeperThreads(heap()->paged_space(OLD_DATA_SPACE));
     StealMemoryFromSweeperThreads(heap()->paged_space(OLD_POINTER_SPACE));
-    heap()->FreeQueuedChunks();
+    return true;
   }
+  return false;
 }
 
 
 intptr_t MarkCompactCollector::
              StealMemoryFromSweeperThreads(PagedSpace* space) {
   intptr_t freed_bytes = 0;
   for (int i = 0; i < FLAG_sweeper_threads; i++) {
     freed_bytes += heap()->isolate()->sweeper_threads()[i]->StealMemory(space);
   }
   return freed_bytes;
 }
 
 
 bool MarkCompactCollector::AreSweeperThreadsActivated() {
   return heap()->isolate()->sweeper_threads() != NULL;
 }
 
 
 bool MarkCompactCollector::IsConcurrentSweepingInProgress() {
   return sweeping_pending_;
 }
 
 
+void MarkCompactCollector::FinalizeSweeping() {
+  ASSERT(sweeping_pending_ == false);
+  ReleaseEvacuationCandidates();
+  heap()->FreeQueuedChunks();
+}
+
+
 void MarkCompactCollector::MarkInParallel() {
   for (int i = 0; i < FLAG_marking_threads; i++) {
     heap()->isolate()->marking_threads()[i]->StartMarking();
   }
 }
 
 
 void MarkCompactCollector::WaitUntilMarkingCompleted() {
   for (int i = 0; i < FLAG_marking_threads; i++) {
     heap()->isolate()->marking_threads()[i]->WaitForMarkingThread();
@@ skipping 298 matching lines @@
 
 #ifdef DEBUG
   ASSERT(state_ == IDLE);
   state_ = PREPARE_GC;
 #endif
 
   ASSERT(!FLAG_never_compact || !FLAG_always_compact);
 
   if (AreSweeperThreadsActivated() && FLAG_concurrent_sweeping) {
     // Instead of waiting we could also abort the sweeper threads here.
-    WaitUntilSweepingCompleted();
+    if (WaitUntilSweepingCompleted()) {
+      FinalizeSweeping();
+    }
   }
 
   // Clear marking bits if incremental marking is aborted.
   if (was_marked_incrementally_ && abort_incremental_marking_) {
     heap()->incremental_marking()->Abort();
     ClearMarkbits();
     AbortCompaction();
     was_marked_incrementally_ = false;
   }
 
@@ skipping 2373 matching lines @@
   heap_->isolate()->inner_pointer_to_code_cache()->Flush();
 
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) {
     VerifyEvacuation(heap_);
   }
 #endif
 
   slots_buffer_allocator_.DeallocateChain(&migration_slots_buffer_);
   ASSERT(migration_slots_buffer_ == NULL);
+}
+
+
+void MarkCompactCollector::ReleaseEvacuationCandidates() {
+  int npages = evacuation_candidates_.length();
   for (int i = 0; i < npages; i++) {
     Page* p = evacuation_candidates_[i];
     if (!p->IsEvacuationCandidate()) continue;
     PagedSpace* space = static_cast<PagedSpace*>(p->owner());
     space->Free(p->area_start(), p->area_size());
     p->set_scan_on_scavenge(false);
     slots_buffer_allocator_.DeallocateChain(p->slots_buffer_address());
     p->ResetLiveBytes();
     space->ReleasePage(p);
   }
@@ skipping 558 matching lines @@
   // the map space last because freeing non-live maps overwrites them and
   // the other spaces rely on possibly non-live maps to get the sizes for
   // non-live objects.
 
   SweepSpace(heap()->old_pointer_space(), how_to_sweep);
   SweepSpace(heap()->old_data_space(), how_to_sweep);
 
   if (how_to_sweep == PARALLEL_CONSERVATIVE) {
     // TODO(hpayer): fix race with concurrent sweeper
     StartSweeperThreads();
     if (FLAG_parallel_sweeping && !FLAG_concurrent_sweeping) {

[Michael Starzinger, 2013/02/21 12:22:09]

How about moving all of this magic into the how_to_sweep variable by introducing
a CONCURRENT_CONSERVATIVE on top of the existing PARALLEL_CONSERVATIVE?

[Hannes Payer (out of office), 2013/02/21 12:52:31]

Done.

       WaitUntilSweepingCompleted();
     }
   }
 
   RemoveDeadInvalidatedCode();
   SweepSpace(heap()->code_space(), PRECISE);
 
   SweepSpace(heap()->cell_space(), PRECISE);
 
   EvacuateNewSpaceAndCandidates();
 
   // ClearNonLiveTransitions depends on precise sweeping of map space to
   // detect whether unmarked map became dead in this collection or in one
   // of the previous ones.
   SweepSpace(heap()->map_space(), PRECISE);
 
   // Deallocate unmarked objects and clear marked bits for marked objects.
   heap_->lo_space()->FreeUnmarkedObjects();
+
+  if (!FLAG_concurrent_sweeping) {

[Michael Starzinger, 2013/02/21 12:22:09]

This is still not entirely correct, it _has_ to depend of the how_to_sweep
variable because that determines how the pages were swept.

[Hannes Payer (out of office), 2013/02/21 12:52:31]

Done.

+    FinalizeSweeping();
+  }
 }
 
 
 void MarkCompactCollector::EnableCodeFlushing(bool enable) {
 #ifdef ENABLE_DEBUGGER_SUPPORT
   if (heap()->isolate()->debug()->IsLoaded() ||
       heap()->isolate()->debug()->has_break_points()) {
     enable = false;
   }
 #endif
@@ skipping 180 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal